Sarcocornia neei: A novel halophyte species for bioremediation of marine aquaculture wastewater and production diversification in integrated systems

The integration of bioremediation systems is one of the most promising techniques to mitigate the environmental impact of aquaculture effluents. Also, it allows nutrient recycling, production diversification, and the creation of high-value by-products. In marine aquaculture, where the implementation of salt-tolerant extractive species is essential, halophyte plants have demonstrated to be optimal candidates for bioremediation of saline aquaculture wastewater. This study aimed to evaluate for the first time the efficiency of Sarcocornia neei (Lag.), a halophyte plant with high adaptability, salinity tolerance and growth potential when irrigated with seawater, in removing nutrients from marine fish aquaculture wastewater and artificial effluents. Two experiments were carried out. In the first one, the growth rate, removal of inorganic nutrients, and accumulation of organic compounds in deep-water hydroponics and sand-substrate systems were evaluated in artificial effluents with different nitrogen and phosphate loads during 70 days. In the second, due to the better performance achieved by S. neei in deep-water systems, its nitrogen removal efficiency and productivity rates were evaluated in deep-water aquaponics with marine aquaculture wastewater and artificial effluents at higher nitrogen loads during 61 days. The highest productivity rates achieved by S. neei (14.41 ± 0.78 kg m⁻²) were obtained in deep-water culture units, reaching 100% plant survival, suggesting that this species is more suitable for its implementation in this type of system. Significant total ammonia nitrogen removal rates were obtained by the plants, achieving a maximum in sand-substrate systems (0.68 ± 0.41 g m⁻² day⁻¹). The results of nitrate removal rates obtained by S. neei (11.25 ± 31.38 g m⁻² day⁻¹) make this species an ideal potential candidate for the removal of this compound present in marine RAS effluents. Accumulation of organic compounds was corroborated by obtaining a significant increase (p < 0.05) in organic N (31.2 ± 0.1 mg g dry weight⁻¹) and organic P (4.0 ± 0.6 mg g dry weight⁻¹) content in plant biomass at the end of the trials. These results indicated that S. neei is a good candidate for its use as a biofilter for marine aquaculture wastewater. Further investigations should be done to analyze possible influences on growth rates and nutrient removal efficiency by adding essential micronutrients, adjusting effluent salinity, and implementing different plant densities. Also, further studies could be interesting to determine the feasibility of long-term integration of a bioremediation system with S. neei associated with marine aquaculture effluents, approaching its application to industrial-scale production systems.